Paper 1: Girish Welling and B. R. Badrinath

A Framework for Environment Aware Applications

In Proceedings of the 17th ICDCS Conference, Baltimore, Maryland, May, 1997

The paper describes a framework for applications that may make use of environmental awareness (e.g. low on memory, low on power, low on bandwidth). Such a mechanism makes sense for a co-operative environment - a single user using a mobile computing device.

Components of the architecture

• Factory: this is the component that generates events.
• Channel: Events pass through this component. Channels are used for multiplexing several events of the same type (e.g. all network events may go through one channel). Channel adds a level of indirection.
• Handler: This component will be part of the application (mostly). This would get events from the channel object & handle them.
• Channel Registrar: Provides a naming service for the channel name-space (the set of all event types like network events, memory events etc).
• Event objects: These are the components that represent physical events. Events are arranged in a hierarchical fashion (like in an OO class hierarchy).

The Channel

• Channels can have policies for delivering events. For example, a low-on-memory event may be delivered only to certain applications & only as long as there is shortage of memory.
• Channels buffer events for new-comers. If an application starts up afresh, it can know the current state of the world (the current environment) by getting stored events from the channel.
• Channels are used for grouping events.

Example Application

Pine, a mailer application is modified to take advantage of environmental awareness. With low bandwidth CDPD connectivity, only the headers of incoming mail is retrieved & outgoing mails are buffered. When high bandwidth WaveLAN connectivity is available, full-fledged access to the mailbox & immediate mail-send are enabled.